1. Field of the Invention
The present invention relates to a method for manufacturing graphene film, a graphene film manufactured by the same, and electronic device comprising the graphene film, which manufacture a graphene film easily detached from a growth substrate with more simplified process and intends to apply its properties such as excellent spatial homogeneity to electronic devices.
2. Background of the Invention
Graphene, a material having useful properties such as very high carrier mobility and optical nonlinearity, is spotlighted as the most prominent material applicable to electronic/photo-electronic devices in future.
Up to date, a lot of studies on methods for preparing or applying various graphene to yield graphene—having improved properties in its nano structure and electrical characteristics such as crystallinity, carrier mobility, and crystal scalability—with high efficiency have been progressed. Especially, the studies have focused on application of graphene including graphene based transparent electrode, channel layer of activation device, battery electrode, femtosecond laser using graphene, and photo-detector and brought valuable results in spite of its short history. However in order to apply the graphene material to electronics and photonics in future, shape control and layer number control of graphene as well as resistance between graphene nano layers are remained as tasks to be overcome.
Besides although it is required to yield graphene with a quality higher than a certain level even in preparing it for applying it in engineering, it has a problem of lower yield and its solution rises as an important task to be solved for commercialization of the graphene material. Along with this, provision of a method to minimize harmful defects on nano structure of graphene and a concrete solution to difficulty in graphene detachment occurring when transferring the synthesized graphene to user defined substrate (a substrate for applying the graphene material) are also required.
Large area graphene embarks a new chapter in application of the graphene material due to its new electrical and structural properties. As methods for preparing this large area graphene, for example, graphitization on a SiC substrate, a method for synthesizing graphene on a nickel catalyst using molten carbon source through chemical vapor deposition (CVD) method and a method for synthesizing graphene on a copper (Cu) catalyst using carbon precursor through CVD method receive attention.
Among these, the CVD method using copper catalyst has been known able to prepare large area single layer graphene with the highest quality up to several μm2 (Yu, Q. et 68-5 2013-10-07 al. Control and characterization of individual grains and grain boundaries in graphene grown by chemical vapor deposition. Nature Mater. 10, 443-449 (2011)).
Growth of graphene using SiC substrate is important from the point that it is possible to form graphene directly on an insulating substrate. However, it has technological limits including high price of the substrate and difficulty in control of homogeneity and layer number of graphene. On the contrary, the graphene synthesis on a copper film is a method receiving attention because it has merits including advantageous price as well as capability to form large area single layer graphene with relatively homogeneous properties. However, it also has demerits such as additional demand for catalyst (copper) removing process and long time required for graphene film transfer process. However as it is a method capable of transfer to various substrates including flexible material, the synthesis of graphene film on a copper substrate has received attention as the most promising graphene synthesis method.
However, it has several problems also, including that transfer of multilayer graphene is difficult; (2) the target substrate should be flat; and (3) there should be strong adhesion between the graphene and the substrate.
Accordingly, methods to apply polymer mediated transfer technique of graphene film have been improved continuously and dry type transfer technique to detach graphene film grown on copper substrate was introduced. In addition, there have been several efforts to improve properties of graphene film grown on the copper substrate by controlling the properties of copper substrate and controlling growth conditions such as growth temperature, gas supply ratio, and pressure. (Li, X. et al., Graphene films with large domain size by a two-step chemical vapor deposition process. Nano Lett. 10, 4328-4334 (2010))